package alg20250211;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Text2 {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        Arrays.sort(nums);
        int n = nums.length;
        List<List<Integer>> ret = new ArrayList<>();
        for (int i = 0; i < n - 3; ) {
            for (int j = i + 1; j < n - 2; ) {
                for (int left = j + 1, right = n - 1; left < right;) {
                    long t = (long)target - nums[i] - nums[j];
                    if(nums[left] + nums[right] > t) right--;
                    else if(nums[left] + nums[right] < t) left++;
                    else{
                        ret.add(new ArrayList<>(Arrays.asList(nums[i], nums[j], nums[left], nums[right])));
                        left++; right--;
                        while(left < right && nums[left] == nums[left - 1]) left++;
                        while(left < right && nums[right] == nums[right + 1]) right--;
                    }
                }
                j++;
                while(j < n - 2 && nums[j] == nums[j - 1]) j++;
            }
            i++;
            while(i < n - 3 && nums[i] == nums[i - 1]) i++;
        }
        return ret;
    }
}
